Abstract : Doppler blood flowmeters have been used to detect intravascular gas bubbles which are considered to be a major cause of decompression sickness. However, observations by various investigators have indicated that other factors such as red cell agglutination, platelet aggregates and coalescence of lipids may be involved in decompression sickness. The possibility of using the Doppler flowmeters to detect such particles in the blood has been investigated theoretically. Experimental results from these devices implanted around the inferior venae cavae of rabbits are presented showing the waveform for bubbles as well as changes which appear in the blood flow waveform during decompression. The latter may indicate aggregation of erythrocytes and/or platelets.